The invention relates to a water-in-hydrocarbon emulsion which is useful as a low emission fuel for compression ignition engines and to a method for forming same.
The impact of incorporating water into the combustion systems of Diesel engines has been presented in technical literature with an important incidence in reduction in exhaust emission rates of nitrogen oxides and particulates and with moderate reductions, and in certain cases with increases, in the exhaust emission rates of hydrocarbons and carbon monoxide. According to various investigations, the effect of reducing peak flame temperatures in the combustion chamber is the dominant cause for lower nitrogen oxide emissions.
The Clean Air Act mandates progressive decreases in smoke, particulate and nitrogen oxide emissions from both stationary and mobile sources. Attempts to address these requirements using water-in-hydrocarbon emulsions have met with very serious technical and economic problems due to the short-term stability of emulsions formed having droplet sizes in the macroemulsion range, and further due to the large quantities of surfactants and cosolvents required to form emulsions having droplet sizes in the microemulsion range.
For example, U.S. Pat. Nos. 4,568,354 and 4,568,355 to Davis et al. are drawn to processes for converting a hazy or potentially hazy water saturated alcohol-gasoline mixture into a clear stable gasoline composition having an improved octane rating. The system so produced has a water content of no more than 1% by volume, and relatively large volumes of non-ionic surfactant are used to produce this system.
Similarly, U.S. Pat. Nos. 4,770,670 and 4,744,796 to Hazbun et al. also disclose the formation of stable microemulsions which contain large amounts of surfactant as compared to the water content.
Other efforts in this area include U.S. Pat. No. 5,104,418, WO 99/35215, U.S. Pat. No. Re. 35,237, U.S. Pat. No. 5,743,922, WO 97/34969, U.S. Pat. No. 5,873,916 and WO 99/13031.
In spite of the disclosures in the a foregoing patents, the need remains in the industry for a water-in-hydrocarbon emulsion which is suitable as a combustible fuel and which contains a desirable amount of water without the need for relatively large amounts of surfactant and/or other stabilizing agents.
It is therefore the primary object of the present invention to provide water-in-hydrocarbon emulsions which are useful as combustible fuels and which are both stable and formed using relatively small amounts of surfactant.
It is a further object or the present invention to provide a method for forming such water-in-hydrocarbon emulsions utilizing a synergetic combination of mixing energy and surfactant package blend.
It is a still further object of the present invention to provide emulsions and methods for forming such emulsions wherein additional combustion properties are incorporated into the fuel through the surfactant package.
Other objects and advantages of the present invention will be readily apparent from a consideration of the following.